diff --git a/src/activitypub/actors.js b/src/activitypub/actors.js
index bd339a7f5d..90fadfe628 100644
--- a/src/activitypub/actors.js
+++ b/src/activitypub/actors.js
@@ -21,6 +21,11 @@ const failedWebfingerCache = TTLCache({
 const activitypub = module.parent.exports;
 
 const Actors = module.exports;
+Actors._followerCache = TTLCache({
+	name: 'ap-follower-cache',
+	max: 5000,
+	ttl: 1000 * 60 * 60, // 1 hour
+});
 
 Actors.qualify = async (ids, options = {}) => {
 	/**
@@ -420,17 +425,22 @@ Actors.assertGroup = async (ids, options = {}) => {
 	return categoryObjs;
 };
 
-Actors.getLocalFollowers = async (id) => {
-	// Returns local uids and cids that follow a remote actor (by id)
-	const response = {
+Actors.getFollowers = async (id) => {
+	/**
+	 * Returns followers by local or remote id. Pass in a...
+	 *  - Remote id: returns local uids/cids that follow
+	 *  - Local id: returns remote uids that follow
+	 */
+	let response = Actors._followerCache.get(id);
+	if (response) {
+		return response;
+	}
+
+	response = {
 		uids: new Set(),
 		cids: new Set(),
 	};
 
-	if (!activitypub.helpers.isUri(id)) {
-		return response;
-	}
-
 	const [isUser, isCategory] = await Promise.all([
 		user.exists(id),
 		categories.exists(id),
@@ -440,10 +450,10 @@ Actors.getLocalFollowers = async (id) => {
 		const members = await db.getSortedSetMembers(`followersRemote:${id}`);
 
 		members.forEach((id) => {
-			if (utils.isNumber(id)) {
-				response.uids.add(parseInt(id, 10));
-			} else if (id.startsWith('cid|') && utils.isNumber(id.slice(4))) {
+			if (id.startsWith('cid|') && utils.isNumber(id.slice(4))) {
 				response.cids.add(parseInt(id.slice(4), 10));
+			} else {
+				response.uids.add(utils.isNumber(id) ? parseInt(id, 10) : id);
 			}
 		});
 	} else if (isCategory) {
@@ -462,6 +472,7 @@ Actors.getLocalFollowers = async (id) => {
 		});
 	}
 
+	Actors._followerCache.set(id, response);
 	return response;
 };
 
diff --git a/src/activitypub/inbox.js b/src/activitypub/inbox.js
index f3413f3f51..ea0e99de35 100644
--- a/src/activitypub/inbox.js
+++ b/src/activitypub/inbox.js
@@ -47,7 +47,7 @@ inbox.create = async (req) => {
 	}
 
 	// Category sync, remove when cross-posting available
-	const { cids } = await activitypub.actors.getLocalFollowers(actor);
+	const { cids } = await activitypub.actors.getFollowers(actor);
 	let cid = null;
 	if (cids.size > 0) {
 		cid = Array.from(cids)[0];
@@ -202,7 +202,7 @@ inbox.update = async (req) => {
 							return await activitypub.notes.assertPrivate(object);
 						}
 
-						const { cids } = await activitypub.actors.getLocalFollowers(actor);
+						const { cids } = await activitypub.actors.getFollowers(actor);
 						let cid = null;
 						if (cids.size > 0) {
 							cid = Array.from(cids)[0];
@@ -387,7 +387,7 @@ inbox.announce = async (req) => {
 	let pid;
 
 	// Category sync, remove when cross-posting available
-	const { cids } = await activitypub.actors.getLocalFollowers(actor);
+	const { cids } = await activitypub.actors.getFollowers(actor);
 	const syncedCids = Array.from(cids);
 
 	// 1b12 announce
@@ -522,6 +522,7 @@ inbox.follow = async (req) => {
 
 		const followerRemoteCount = await db.sortedSetCard(`followersRemote:${id}`);
 		await user.setUserField(id, 'followerRemoteCount', followerRemoteCount);
+		activitypub.actors._followerCache.del(id);
 
 		await user.onFollow(actor, id);
 		activitypub.send('uid', id, actor, {
@@ -613,6 +614,8 @@ inbox.accept = async (req) => {
 				db.sortedSetAdd(`followersRemote:${actor}`, timestamp, `cid|${id}`), // for notes assertion checking
 			]);
 		}
+
+		activitypub.actors._followerCache.del(actor);
 	}
 };
 
@@ -650,6 +653,7 @@ inbox.undo = async (req) => {
 					const followerRemoteCount = await db.sortedSetCard(`followerRemote:${id}`);
 					await user.setUserField(id, 'followerRemoteCount', followerRemoteCount);
 					notifications.rescind(`follow:${id}:uid:${actor}`);
+					activitypub.actors._followerCache.del(id);
 					break;
 				}
 
diff --git a/src/activitypub/notes.js b/src/activitypub/notes.js
index 3cef55670e..32d801f57e 100644
--- a/src/activitypub/notes.js
+++ b/src/activitypub/notes.js
@@ -506,7 +506,7 @@ Notes.updateLocalRecipients = async (id, { to, cc }) => {
 
 		const followedUid = await db.getObjectField('followersUrl:uid', recipient);
 		if (followedUid) {
-			const { uids: followers } = await activitypub.actors.getLocalFollowers(followedUid);
+			const { uids: followers } = await activitypub.actors.getFollowers(followedUid);
 			if (followers.size > 0) {
 				followers.forEach((uid) => {
 					uids.add(uid);
@@ -590,7 +590,7 @@ Notes.syncUserInboxes = async function (tid, uid) {
 	});
 
 	// Category followers
-	const categoryFollowers = await activitypub.actors.getLocalFollowers(cid);
+	const categoryFollowers = await activitypub.actors.getFollowers(cid);
 	categoryFollowers.uids.forEach((uid) => {
 		uids.add(uid);
 	});
diff --git a/src/activitypub/out.js b/src/activitypub/out.js
index 701464ba8c..dbe3a3e8e4 100644
--- a/src/activitypub/out.js
+++ b/src/activitypub/out.js
@@ -513,6 +513,7 @@ Out.undo.follow = enabledCheck(async (type, id, actor) => {
 			db.sortedSetRemove(`followersRemote:${actor}`, `cid|${id}`),
 		]);
 	}
+	activitypub.actors._followerCache.del(actor);
 });
 
 Out.undo.like = enabledCheck(async (uid, pid) => {
diff --git a/src/categories/index.js b/src/categories/index.js
index 047de142c8..ed0b60b08f 100644
--- a/src/categories/index.js
+++ b/src/categories/index.js
@@ -58,7 +58,7 @@ Categories.getCategoryById = async function (data) {
 		Categories.getTopicCount(data),
 		Categories.getWatchState([data.cid], data.uid),
 		getChildrenTree(category, data.uid),
-		!utils.isNumber(data.cid) ? activitypub.actors.getLocalFollowers(data.cid) : null,
+		!utils.isNumber(data.cid) ? activitypub.actors.getFollowers(data.cid) : null,
 	];
 
 	if (category.parentCid) {